Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$128.51	11.190%	$142.8903	$142.89	$142.90	$142.90
Purchase #2	$213.52	9.311%	$233.4008	$233.40	$233.40	$233.40
Purchase #3	$70.74	12.481%	$79.5691	$79.57	$79.55	$79.60
Purchase #4	$119.63	10.668%	$132.3921	$132.39	$132.40	$132.40
Purchase #5	$153.74	9.800%	$168.8065	$168.81	$168.80	$168.80
Purchase #6	$133.89	3.644%	$138.769	$138.77	$138.75	$138.80
Purchase #7	$131.27	9.641%	$143.9257	$143.93	$143.95	$143.90
7 purchase totals =	$951.30		$1,039.7535	$1,039.76	$1,039.75	$1,039.80